1. Field of the Invention
The invention relates generally to micro-electro-mechanical systems devices or MEMS devices. More particularly, the invention relates to a micro-electrical mechanical coolant pump and cooling assembly for the removal and transfer of heat generated by one or more integrated circuit chips (ICs) to an external heat exchanger.
2. Description of the Related Art
Microelectronic integrated circuit chips, or ICs, require improved cooling methods for heat removal. Prior art methods of IC cooling use a pressurized fluid, or coolant, flowing across or adjacent the surface of an IC. Heat generated by the operation of the IC is absorbed and transferred to the coolant. The heated coolant is then circulated to an external heat exchanger in another part of the system where the heat is removed before it is circulated back to the IC(s) in a manner similar to that of an internal combustion engine radiator assembly.
Very small cooling system feature size can be achieved using MEMS technology to fabricate pump assemblies for use in IC cooling or for insertion into three-dimensional micro-electronic modules such as those disclosed in U.S. Pat. No. 6,967,411 to Eide, U.S. Pat. No. 6,806,559 to Gann, et al., U.S. Pat. No. 6,784,547 to Pepe, et al., U.S. Pat. No. 6,734,370 to Yamaguchi, et al., U.S. Pat. No. 6,706,971 to Albert, et al., U.S. Pat. No. 6,117,704 to Yamaguchi, et al., U.S. Pat. No. 6,072,234 to Camien, et al., U.S. Pat. No. 5,953,588, to Camien, et al., U.S. Pat. No. 4,953,533 to Go, U.S. Pat. No. 5,104,820 to Go, and U.S. Pat. No. 5,688,721 to Johnson, all assigned to common assignee, Irvine Sensors Corp. and each of which is incorporated fully herein by reference.
Established MEMS fabrication processes can create high aspect ratio features, (i.e., vertical sidewalls, valve members, flexures, drive mechanisms or micro-channels) with dimensions of a few microns. MEMS fabrication and feature size attributes provide the ability to create a MEMS micro-pump that can circulate a coolant through a system in a very small volume for IC heat transfer to an external heat exchanger.
The use of MEMS-fabricated micro-channels for heat absorption and removal from microelectronic devices is thermally efficient due to the large surface area available for heat exchange. However, the high flow resistance introduced by a very small flow cross-section (e.g., 10 microns or less) of a micro-channel structure presents a problem for practical pumping devices. Where an external central coolant pump (i.e., separate from the IC to be cooled) is required for the circulation of a coolant through several IC components, there is a relatively high fluid pressure necessary to maintain such coolant flow. This, in turn, requires the cooling system be capable of withstanding high pump pressure at the risk of coolant line breakage and leakages. Further, the pumping pressure requirement changes with a change in the number of cooled components, making the control of coolant flow and temperature control more difficult.
This problem can be solved if a pump is provided that is small enough to allow its positioning in very close proximity to every channel in a micro-channel MEMS structure. By having the pump assembly proximal the micro-channels, only the micro-channel(s) are required to withstand the pumping pressure while the coolant pressure in the rest of the cooling system is maintained at relatively low pressure levels. Because the remaining elements of the cooling system are not required to withstand high continuous pressure levels, their reliability and manufacturability are improved.
What is needed is a micro-pump structure for the cooling of one or more ICs that possesses the above desirable attributes and overcomes the aforementioned problems.